Drilling and stud setting apparatus and method

ABSTRACT

THIS DISCLOSURE IS A METHOD AND APPARATUS FOR FACILITATING THE DRIVING AND ANCHORING OF A TOOL, BOLT, OR FASTENING DEVICE IN A REFRACTORY MATERIAL OR OTHER MATERIAL WITH THE RESULT THAT THE TOOL, BOLT OR FASTENING DEVICE IS FIRMLY FASTENED IN THE MATERIAL. REFERENCE IS MADE TO THE CLAIMS FOR A LEGAL DEFINITION OF THE INVENTION.

June 29, 1971 R c. M MASTER ETAL 3 58,

DRILLING AND STUD SETTING APPARATUS AND METHOD Filed Apl 'il 28, 1969 3 Sheets-Sheet 1 H/VIZI'T/(IH. ROBERT C. M MASTER CHARLES C. LIBBY KEITH LIKBNS June 29, 1971 c, m MASTER ErAL 3,588,996

DRILLING AND STUD SETTING APPARATUS AND METHOD Filed April 28, 1969 I5 Sheets-Sheet 2 FIG. 30

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KEHH ILEKINS ATTORNEY United States Patent O US. Cl. 29-432 Claims ABSTRACT OF THE DISCLOSURE This disclosure is a method and apparatus for facilitating the driving and anchoring of a tool, bolt, or fastening device in a refractory material or other material with the result that the tool, bolt or fastening device is firmly fastened in the material. Reference is made to the claims for a legal definition of the invention.

CROSS REFERENCES RELATED TO APPLICATIONS There is disclosed in Pat. No. 3,368,085, for Sonic Transducer by Robert C. McMaster and Berndt B. Dettloff, a resonanbstructure transducer capable of delivering high power energy in an acoustical range. This transducer provides a continuous high mechanical output with an exceptionally high efiiciency of energy transformation. The transducer is rugged, very simple in design, and capable of repetitive manufacture. Further, the transducer is readily adaptable for use as a hand tool. The disclosure of patent application, S.N. 713,031, filed May 20, 1968, for Sonic Transducer Assembly by Robert C. McMaster, Charles C. Libby, and Keith Likins illustrates how the aforementioned transducer may be adapted for use as a hand tool.

There is further disclosed in Pat. No. 3,396,285, for Electromechanical Transducer by Hildegard M. Minchenko, a resonant structure transducer capable of delivering extremely high power, i.e., measurable in horsepower (or kilowatts) at an acoustical frequency range. The principle underlying the high power output is in the structural arrangement of the components immediately associated with the piezoelectric driving elements. In theory and practice, the piezoelectric elements are under radial and axial pressure that assure that they do not operate in tension even under intense sonic action. Significantly, the structural design of this transducer, that permits the extraordinary power output from the driving elements,

resides in the novel method of clamping the piezoelectric elements both radially and longitudinally (axially). In this way the acoustic stresses in the piezoelectric elements are always compressive, never tensile, even under maximum voltage excitation.

The transducer disclosed in the aforementioned patent is intended, and therefore utilized, to deliver a steady state signal. That is, the piezoelectric assembly is a component of a resonant structure that will produce a mechanical vibratory output at the frequency of the driving electrical signal and vice versa.

In the copending patent application, S.N. 713,035, filed Mar. 14, 1968, for Hot Rolling and Deformation of Metals Using Sonic Power, by Robert C. McMaster, vibratory energy from an electromechanical sonic trans ducer is applied to the work material. Vibratory energy is transmitted efficiently through the material where the stresses resulting from the vibrational energy are less than the elastic limit of the material. Where the vibrational energy input from an electromechanical sonic transducer creates stresses which exceed the elastic limit of the material the vibrational energy is no longer efliciently transmitted; rather, a large amount of the vibrational energy is transformed into heat by mechanical hysteresis. By this process enough heat can be generated to soften steel and melt other metals and alloys.

In the copending patent application for Sonic Transducer Apparatus, S.N. 605,284, filed Dec. 28, 1966, by Robert C. McMaster, Charles C. Libby, and Hildegard M. Minchenko, there is disclosed means of utilizing the aforementioned high-power, high Q electromechanical transducer in a work environment. The apparatus consists of impact coupling the high-power electromechanical transducer to a tool in a work environment. The significant feature of the invention of the last-mentioned patent application is that the tool does not form a part of the transducer resonant structure. This feature permits the transducer to develop fu1l-power capability at its resonant frequency.

BACKGROUND OF INVENTION, PRIOR ART In the conventional type of refractory anchor several operations are required to set an anchor. A standard anchor, for instance the Rawl saber-tooth, requires the following operations to set: insert saber-tooth in chuck, drill saber-tooth to proper depth, clean saber-tooth and hole, insert expander plug, re-insert saber-tooth assembly in hole, hammer till saber-tooth anchor assumes proper depth again, remove hammer, break off taper with sharp blow, eject taper from chuck. This reasonably complicated procedure has eight separate operations.

In conventional practice, lead is sometimes used to anchor bolts into refractory materials. The bolt is merely placed into a hole in the refractory and lead is cast into the hole. When the lead solidifies, the anchor is well set. Lead, though, has certain disadvantages because of its softness and can result in loosening of the bolt should much vibration be present in the anchoring system. Alloys that expand on cooling are useful for forming a tight bond between a refractory material and an anchor set in said refractory material. Low melting alloys of bismuth are useful in this regard in that they expand on cooling.

SUMMARY OF THE INVENTION The present invention is a process and apparatus which utilizes a high-power electromechanical sonic or ultrasonic transducer to provide vibratory-mechanical energy to drive a drilling tool (which can be a simple bolt or stud) into a refractory material. The electromechanical transducer transforms electrical energy into vibratorymechanical energy manifested by motion at the tip of the transducer in the axial direction. Intermittent static force applied to the transducer is transmitted to the drilling tool through the tip of the transducer. In this way the intermittent static force in conjunction vwith the vibratory-mechanical energy concentrated at the tip of the transducer causes the refractory material under the drilling tool to be fractured and pulverized. Since the movement of the drilling tool is restrained to movement in the axial direction which is substantially perpendicular to the surface of the refractory material, only the refractory material directly under the tool is pulverized thereby enabling the tool to drill straight into the refractory material.

It is significant that the apparatus and process of the present invention permits a hole to be drilled in refractory material with a drilling tool that does not rotate. This feature of the present invention enables holes of irregular shapes to be drilled in refractory material. Holes of irregular shape are useful to solidly anchor a stud or other implement in a refractory material by causing a metal alloy to melt and surround the tool. This is due to the fact that the irregular shape of the hole militates against the anchor or stud turning.

After the drilling tool has bored into the refractory material to the desired depth, the tool is removed and a metal alloy, preferably a low-melting alloy such as a bismuth alloy or a zinc alloy, is inserted in the cavity. The drilling tool is positioned against the metal alloy in the cavity, a constant static force is then exerted on the transducer which is transmitted through the transducer tip to the drilling tool, and the electromechanical transducer is activated. The combination of the constant static stress in the tool and the dynamic stresses created by the vibratory-mechanical energy cause mechanical hysteresis to occur in the tool thereby liberating heat in the tool. This phenomenon in conjunction with frictional heating causes the metal alloy to at least partially melt and the vibratory mechanical energy agitates the melted metal alloy as the applied constant static force squeezes the drilling tool past the metal alloy to the bottom of the hole. Agitation of the melted metal alloy due to the action of the vibratory-mechanical energy transmitted to the alloy through the drilling tool facilitates penetration of the melted metal alloy into the interstices of the refractory material making an excellent bond therewith. Further, any dust which remained in the hole from the drilling operation is agitated and mixed with the melted metal alloy thereby eliminating the deleterious lubricating effect which the dust could have on the alloy-refractory or alloy-tool interfaces. Removal of the electromechanical transducer from contact with the drilling tool prevents further heating action and allows the drilling tool to cool. Upon cooling, the solidification and expansion (in the case of bismuth alloys) of the melted alloy firmly aflixes the drilling tool in the refractory material.

OBJECTS The present invention has for its principal object a system and method for setting a stud in refractory materials.

Another object of the invention is to reduce the number of operations necessary to set a stud in refractory materials.

Another object of the invention is to provide a system and method to increase the speed and facility with which holes can be drilled in refractory and other materials.

Another object of the invention is to provide a system and method which may use any of a variety of implements of preselected geometries as the working tool.

Another object of the invention is to provide a system and method for sonically melting metal alloy to set a stud in a hole in refractory materials.

A further object of the invention is to eliminate the need for separate facilities for melting metal alloy.

Still another object of the invention is to provide a system and method which will agitate melted metal alloy and facilitate penetration thereof into the refractory making a secure alloy-masonry bond.

For a complete understanding of the invention, together with other objects and advantages thereof, reference may be made to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the preferred embodiment of the masonry stud setting device in position to drive a drilling tool, in this case an ordinary hex head bolt, into a block of refractory material;

FIG. 2 illustrates the positioning of the planar surface of a drilling tool, in this case an ordinary hex head bolt, head positioned against the surface of a refractory material with an electromechanical sonic or ultrasonic transducer assembly positioned to drive the hex head bolt into the refractory material thereby making a hole;

FIG. 2a illustrates the drilling tool, here an ordinary hex head bolt, with a hollow cylinder of metal alloy fitted around its shank;

FIG. 3 illustrates a drilling tool, here an ordinary hex head bolt, driven into the refractory material to a desired depth;

FIG. 3a illustrates the drilling tool, here an ordinary hex head bolt, having a hollow cylinder of metal alloy around its shank, driven into the refractory material to the desired depth;

FIG. 4 illustrates a hollow cylinder of metal alloy placed in the hole drilled using the drilling tool, here an ordinary hex head bolt, and electromechanical transducer, the transducer positioned to sonically excite the bolt, generate heat and melt the metal alloy;

FIG. 5 illustrates the bolt set in the refractory after the metal alloy has been sonically melted, sonically agitated, and solidified;

FIG. 6 is an illustration of how the drilling rate varies with tool length;

FIG. 7 is an illustration of the oscillatory action of various elements of the sonic drilling system; and,

FIG. 8 illustrates the physical relationship of the elements of the drilling system, not including the gross motion of the transducer.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring generally to FIG. 1 there is illustrated the preferred embodiment of the present invention. The apparatus of the present invention is used to effect a novel drilling and anchoring process for securely alfixing a stud or other implement in a refractory material. The apparatus comprises an electromechanical transducer 1 which is supported by nodal supports 15 attached to the node point 16 of the electromechanical transducer 1. A linearmotion bearing assembly 3 is securely attached to the structure 15. The assembly 3 is secured to the nodal support 15 by means comprising snap rings 17 attached to the linear-motion bearing assembly 3 and the nodal support 15. A bushing 6 in the linear-motion bearing assembly 3 is a guide for the drilling tool 4 which is shown positioned against the refractory material 5 to be drilled.

Details concerning the electromechanical transducer utilized in the present invention are disclosed in Pat. No. 3,368,085, for Sonic Transducer by Robert C. Mc- Master, and Berndt B. Dettlolf. The adapation of the sonic transducer for use as a hand-held tool is facilitated by a shroud which is designed to enclose the transducer, support the transducer, and eliminate any electrical shock hazard associated with the transducer.

The electromechanical transducer 1 transforms an alternating-polarity input current into mechanical energy, the mechanical energy being concentrated at the tip of the electromechanical transducer 1 and being manifested by motion colinear with the axial direction of the transducer 1 (the axis referred to is the axis of symmetry of the electro-mechanical transducer 1). The energy so concentrated at the tip of the electromechanical transducer 1 is, then, vibratory in nature. It is this vibratory-mechanical energy transmitted from the tip of the transducer 1 to the drilling tool 4, which is the energizing force which drives the drilling tool 4, into the refractory material 5 thereby making a hole. The structure of the electromechanical transducer is resonant, or nearly so, at the frequency of the alternating-polarity input current. Of significance in the operation of the electromechanical transducer 1 is the fact that no direct coupling of the tip of the electromechanical tranducer to either the drilling tool 4 or to the refractory material 5 occurs. There is substantial freedom of movement by the drilling tool between the tip of the electromechanical transducer and the refractory material 5. Accordingly, the drilling tool 4 and the refractory material (workpiece) do not constitute added structure to the electromechanical tarnsducer 1 and, therefore, have no effect on the resonant length and frequency of the electromechanical transducer 1.

The bushing 6 of the linear-motion bearing assembly 3 is a guide for the drilling tool 4. One end of the drilling tool 4 is fittted through the cylindrical aperture in the bushing 6 of the linear-motion bearing assembly 3; that end of the drilling tool 4 contacts the tip of the transducer. The drilling tool 4 and the bushing 6 make a sliding fit. The sliding fit arrangement restrains the drilling tool 4 from shifting position or canting. That is, the linear-motion bearing assembly 3 constrains the movement of the tool to movement coincidental with the axial movement of the tip of the electromechanical transducer 1. Restraining the movement of the drilling tool 4 to movement in the axial direction is very important as this is a key factor in maintaining dimensional accuracy while drilling a hole in refractory materials and other materials. Restraining the drilling tool to axial movement prevents the drilling tool 4 from wandering.

In the system and method of the present invention it is significant that the configurations of the drilling tool 4 that are most efficient are those configurations which have a substantially planar surface contacting the refractory material 5 to be drilled. That is, the drilling tool 4 of the system of the present invention operates much better with a drilling tool 4 that has blunt (substantially planar) cutting surface as opposed to conventional implements which are used for drilling refractory material. Most conventional drilling implements have a pointed cutting surface or a cutting edge which drills or cuts with a rotary motion. The system and process of the present invention, however, is not dependent on a drilling implement with a pointed cutting surface or a cutting edge. Further, the drilling tool 4 of the system and the process of the present invention does not even rotate.

Advantages may be derived from the last-mentioned feature of the present invention. The fact that the drilling tool 4 need not rotate in order to drill a hole in a refractory material enables the system and process of the present invention to be used to bore holes of irregular shapes in refractory material. For example, holes can be drilled which have a perimeter geometry of not only a circle but also a triangle, a rectangle, a hexagon, a trapezoid, or any conceivable irregular shape. The drilling tool 4 may, in fact, consist of an ordinary hex head bolt, a screw, or any other implement having a substantially planar surface which can be utilized as the cutting surface. In the case of the hex head bolt, FIGS. 1 through 5 illustrate how a hex head bolt 4 can be positioned to perform the drilling operation. The substantially planar surface of the hex head bolt is positioned against the refractory material 5 to be drilled, the threaded end of the hex head bolt being fitted through the cylindrical aperture of the bushing 6. In fact, the hex head bolt 4 makes a convenient and inexpensive drilling tool 4 while doubling as a stud which can be anchored in the refractory material. 5. After a hole is drilled with the hex head bolt 4 it is secured in the hole in the refractory material 5 by melting and flowing (after removal of bolt 4 from the hole) a metal alloy around the bolt 4. The hexagonally shaped hole acts essentially as a wrench on the hex head of the hex head bolt thereby militating against the hex head bolt turning in the refractory material 5. This feature gives added utility and permanence to a stud installation using the system and method of the present invention. Of course, the invention is not limited to anchoring a hex head bolt in refractory material. Other implements of special design for performing specialty jobs can readily be adapted for use with the system and method of the present invention.

Examples of only a few of the manifold configurations which specialty drilling tools or implements might take would be implements for securing female threads in a refractory material, securing a hanging hook in a refractory material, or securing any implement in refractory material which is now secured using conventional means. Further, the ability to drill irregularly shaped holes with the system and process of the present invention can be of importance in utilizing some specialty implement. An irregularly shaped hole is, in and of itself, of utilitarian significance for many applications.

In operation, the drilling tool 4 is fitted into the bushing 6 as described hereinabove. The electromechanical transducer 1 and drilling tool 4 are positioned over and substantially perpendicular to the refractory material 5 to be drilled. The substantially planar surface of the drilling tool 4 is positioned against the refractory material 5 at the point to be drilled. A static force F is exerted on the electromechanical transducer 1 at the node 16 thereof. This static force F is transmitted through the tip of the structure of the electromechanical transducer 1 to the drilling tool 4 thereby trapping the drilling tool 4 between the tip and the refractory material 5. The end of the drilling tool 4 which is fitted through the bushing 6 is in contact with the transducer tip. When an alternatingpolarity input current at the resonant frequency of the electromechanical transducer 1 is fed into the electromechanical transducer 1, the resulting vibratory-mechanical energy concentrated at the tip of the electromechanical transducer 1 is transmitted to the drilling tool 4. The static force P which was initially applied to the drilling tool 4 through the structure of the electromechanical transducer 1 is relaxed momentarily after the drilling tool 4 has become excited with the vibratory-mechanical energy. Static force F is intermittently applied to the drilling tool 4 through the electromechanical transducer 1. Intermittent application of static force F increases the rate at which a hole is drilled in refractory material 5.

After the drilling operation has been completed in accordance with the aforedescribed apparatus and method or otherwise, the drilling tool 4 or conventional drilling implement is removed from the hole. Refractory particles remaining in the hole may be removed or not at the option of the operator. It has been found that holes drilled using the apparatus and method of the present invention contain few particles and little dust as compared with the holes drilled with conventional equipment. The vibratorymechanical agitation of the drilling tool 4 during the drilling operation utilizing the present invention tends to expel the particles and dust from said hole. Refer to FIG. 3 for an illustration of the elements of the apparatus and their positions when the drilling operation has been completed and prior to removal of the drilling tool 4 from the hole.

With the apparatus as illustrated in FIG. 3, the drilling tool 4 must be removed from the hole. A metal alloy slug 13 is then placed in the hole in the refractory material 5. The metal alloy slug 13 may be any alloy but is preferably an alloy of bismuth, a metal which expands on cooling. The metal alloy slug 13 may be either a hollow cylinder as shown or may be solid or assume any convenient geometry. The drilling tool 4 and electromechanical transducer 1 are positioned over the metal alloy slug 13, the substantially planar surface of the drilling tool 4 contacting the metal alloy slug 13. A constant static force is applied to the electromechanical transducer 1 and thereby transmitted through the tip of the electromechanical transducer 1 to the drilling tool 4. The electromechanical transducer is activated by feeding an alternating-polarity input current into the electromechanical transducer 1 at its resonant frequency thereby generating vibratory-mechanical energy manifested by axial motion at the tip of the electromechanical transducer 1; the axial motion is oscillatory in nature and substantially perpendicular to the surface of the metal alloy 13. The vibratory-mechanical energy generated by the electromechanical transducer 1 is transmitted to the drilling tool 4 via the tip of the electromechanical transducer 1. The electromechanical energy so transmitted to the drilling tool 4 establishes dynamic stresses within the drilling tool '4. Likewise, the constant static force applied to the electromechanical transducer 1 and transmitted to the drilling tool 4 creates a constant stress level in the drilling tool 4. The constant stress combines with the dynamic stress created in the drilling tool 4 resulting in mechanical hysteresis and the liberation of heat. Heat is also generated by high-velocity friction attributable to the rapid cyclic acceleration of the tool 4 against the metal alloy 13 and the refractory material 5.

The constant stress and vibratory-mechanical energy are applied to the drilling tool 4 for a sufficient time to allow enough heat to build up in the drilling tool 4 to melt or partially melt the metal alloy 13 with which the drilling tool 4 is in contact. When the drilling tool 4 reaches the requisite temperature the metal alloy 13 in contact with the drilling tool 4 melts. The constant static force which is applied to the electromechanical transducer 1 and transmitted to the drilling tool 4 forces the drilling tool 4 past the melted or partially melted metal alloy 13 until the drilling tool 4 reaches the bottom of the hole. The melted or partially melted metal alloy 13 is agitated by the vibratory-mechanical energy which is applied to the drilling tool 4 and then transmitted to the melted metal alloy 13. The agitation flows the melted or partially melted metal alloy and mixes any residual dust in the hole with the melted metal alloy 13. The agitation facilitates the How and penetration of the melted metal alloy 13 into the interstices of the refractory material 5.

The electromechanical transducer 1 is removed from contact with the drilling tool 4 leaving the drilling tool 4 in place surounded by the melted metal alloy 13. Upon removal of the constant static force and the source of the vibratory-mechanical energy the electromechanical transducer 1, mechanical hysteresis, high-velocity friction, and, hence, the liberation of heat in the drilling tool 4 ceases to occur. This allows the melted metal alloy 13 to cool and solidify thereby solidly locking the drilling tool 4 in place. Reference is made to FIG. 5 which illustrates the drilling tool 4 secured in the refractory material 5.

The same result, anchoring a drilling tool 4 in a refractory material 5, may be achieved by an alternative method. Reference is made to FIG. 2a where a hollow cylindrical slug 13 of low-melting alloy 13 is shown positioned over the upper portion of an inverted T shaped drilling tool 4, a common hex head bolt 4. The metal alloy may be cast about the drilling tool 4 or may be so positioned by using a prefabricated hollow cylinder making a press fit or a sliding fit with the drilling tool 4. By using the drilling tool 4, 13, as illustrated in FIG. 2a, the need for removing the drilling tool 4, 13 after the drilling operation has produced a hole in the refractory material 5 of the desired depth is eliminated. FIG. 3a illustrates. a hole which has been completed using the drilling tool 4, 13

illustrated in FIG. 2a. The drilling operation is accomplished as in the first-described method by applying an intermittent static force to the electromechanical transducer 1 and transmitting the intermittent static force to the drilling tool 4. Simultaneously, the electromechanical transducer 1 is excited by an alternating-polarity current which produces vibratory-mechanical energy in the electromechanical transducer 1, the vibratory-mechanical energy likewise being transmitted to the drilling tool 4.

Since the metal alloy 13 is already in position in the hole when the drilling tool 4, 13 of FIGS. 2a and 3a is used to drill a hole in refractory material 5, it is not necessary to remove the drilling tool 4, 13 from the completed hole in order to complete the anchoring operation. Once the hole has been drilled to the desired depth as illustrated in FIG. 3a, constant static force is applied to the electromechanical transducer 1 in lieu of the intermittent static force. Replacing the intermittent static force used in the drilling operation with the constant static force causes the resultant constant stress created in the drilling tool 4, 13, to be combined with the dynamic stresses in the drilling tool 4, 13. This combination of stresses produces mechanical hysteresis thereby liberating heat in the tool 4, 13. The heat generated in the drilling tool 4, 13 by the mechanical hysteresis and by high-velocity friction melts Cit the metal alloy 13 which surrounds the drilling tool 4. The metal alloy 13 is melted or partially melted and agi tated by the vibratory-mechanical energy which flows the melted metal alloy 13 and facilitates penetration of the metal alloy 13 into the interstices of the refractory material 5. The electromechanical transducer 1 is then removed from contact with the drilling tool 4 leaving the drilling tool 4 in its position in the hole. With the removal of the constant static stress and the source of vibratory-mechanical energy, the electromechanical transducer 1, heat ceases to be liberated in the drilling tool 4. Hence, the melted metal alloy 13 is allowed to cool and solidify thereby locking the drilling tool 4 securely in the hole in the refractory material 5. Reference is made to FIG. 5 for an illustration of the drilling tool 4 permanently secured in the hole in the refractory material 5 after the melted or partially melted metal alloy 13 has solidified upon cooling. The end result as illustrated in FIG. 5 is the same for either of the described methods of melting and flowing the metal alloy 13 around the drilling tool 4 to afiix the drilling tool 4 securely in the hole.

It should be noted that the foregoing description has referred to drilling and setting an anchor, stud, or other implement in a refractory material. In order to utilize the method of melting the metal alloy 13 as aforedescribed, the drilling tool 4 or implement must be set in a material of a refractory nature, i.e., a material that does not absorb a substantial amount of heat. Materials which are not of a refractory nature act as heat sinks and prevent the metal alloy from attaining its melting point. It should be noted that with appropriate modifications, the present invention can be used for other applications such as to facilitate the driving of nails into hard wood by generating heat and thereby burning or charring said woodin lieu of drilling a pilot hole.

The drilling operation of the present invention is analogous to the drilling operations performed with conventional apparatus and processes. An analogy may be drawn between the present invention and a conventional pneumatic hammer for breaking pavement or to a common hammer for manually impacting a star-drill to penetrate a refractory material such as a masonry wall. In the case of the hammer and star-drill, the star-drill is impacted with a single blow per cycle of motion of said hammer. Each time the star-drill is impacted by the hammer the refractory material is in turn impacted by the star-drill. In the system of the present invention the tip of the electromechanical transducer 1 and the axial motion thereof is analogous to the conventional hammer and the cycle of motion of said hammer, respectively. Distinctive of the process for drilling with the system of the present invention is the fact that the hammer or electromechanical transducer 1 tip does not strike the work a single blow per cycle of motion of the electromechanical transducer 1 tip. Further, while the cycle of motion of a conventional hammer may be readily measurable in inches, the cycle of axial motion of the electromechanical transducer I tip measures only about 0.0035 inch at a typical resonant fre quency of approximately 10,000 cycles per second. During the drilling process of the present invention the drilling tool 4 is impacted at a rate of up to 10,000 blows per second for brief intervals.

The energy of the hammer and star-drill system is the gross motion of the hammer as supplied by the craftsman holding and swinging the hammer. The system and method of the present invention utilizes electrical energy to produce axial motion at the tip of the electromechanical transducer 1 which is the source of mechanical energy used for driving the drilling tool 4 of the present invention into the refractory material 5. The drilling process of the present invention is essentially a spring-mass system comprising the oscillatory (gross) motion of the transducer mass 1, the mass of its supporting structure 15, enclosure, and the drilling tool 4. The spring of the spring-mass system is the resilient action of the impacted drilling tool 4 as it rapidly oscillates in free flight between the resonant electromechanical transducer I tip and the refractory material surface 5. Since static force is intermittently applied to the electromechanical transducer 1, the drilling tool 4 is not in contact with the top of the electromechanical transducer 1 for relatively long periods of time. That is, while the tip of the electromechanical transducer 1 typically strikes said drilling tool 4 approximately 50 times per second, the drilling tool 4 spends a greater period of time in free flight between the tip of the electromechanical transducer 1 and the refractory material 5 surface than it does in contact with the tip.

Hereinabove, in conjunction with the drilling operation, the drilling tool 4 was trapped between the electromechanical transducer I tip and the refractory material 5 to be drilled. The trapping of the drilling tool 4 between the electromechanical transducer 1 is important in achieving proper drilling action. The drilling action consists of the manner in which the drilling tool 4 performs work on the refractory material 5. The drilling tool 4 moves between the refractory material 5 and the tip of the electromechanical transducer 1. The forward and re turn motion is taken up by the drilling tool 4. That is, the drilling tool 4 bounces back and forth within the confined region with each impact. The impacts of the drilling tool 4 relative to the refractory material 5 do not necessarily occur with each forward movement of the tip of the electromechanical transducer 1. The relative motion between the drilling tool 4 and the tip of said electromechanical transducer 1 may occur (1) due to the compression of the drilling tool 4 at the instant of the impact or (2) due to this compression plus a gross motion of the mass of the drilling tool 4. In either case the motion of the drilling tool 4 causes the drilling tool 4 to disconnect from the tip of the electromechanical transducer 1. Referring again to the drilling action, there are several motions occurring at different frequencies. Certain of the motions are intermittent; some motions are vibratory or oscillatory in nature, a gross movement of the drilling tool 4 (all molecules of a structure moving together) being detectable; and, some motions of the drilling tool 4 are of a resonant type, nodes being observable (parts of the structure not in motion). These various motions are all closely interrelated and derive their energy from a single source, the electromechanical transducer 1.

FIG. 8 schematically illustrates the physical relationship of the various elements of the present invention. As shown in FIG. 8, distance 14 is the total displacement of the tip of the electromechanical transducer 1 during each cycle of axial motion at the resonant frequency of the transducer 1. Distances 11 and 12 are equal and represent the displacement of the drilling tool 4 while the drilling tool 4 is in free flight. When static force is applied to the electromechanical transducer 1 making the tip of the electromechanical transducer 1 contact the drilling tool 4 thereby driving the drilling tool 4 against the refractory material 5, an interference between the drilling tool 4 and the tip of the electromechanical transducer 1 occurs. That is, the drilling tool 4 is in contact with the refractory material and the tip of the electromechanical transducer 1 is in contact with the drilling tool 4. This interference initiates and sustains the aforementioned spring-mass oscillatory motion of the system of the present invention. That is, the vibratory energy of the electromechanical transducer 1 initiates the spring'mass Oscillatory motion when the drilling tool 4 initially interferes with the electromechanical transducer 1 tip motion. The spring-mass oscillatory motion is maintained by periodic interference which occurs at the extreme downward (toward the refractory material 5) position of the tip of the electromechanical transducer and when intermittent static force is being applied to the electromechanical transducer 1, thereby forcing the electromechanical transducer 1 tip into momentary intimate contact with the drilling tool 4.

Resonant vibration is initiated in the drilling tool 4 itself. The resonant vibration is caused by the periodic pulses of high frequency impacts (up to 10,000 per second) with the tip of the electromechanical transducer 1. The periodic pulses occur once each cycle of gross motion of the electromechanical transducer 1. It has been found that the resonant frequency of the electromechanical transducer 1. The periodic pulses occur once each cycle of gross motion of the electromechanical transducer 1. It has been found that the resonant frequency of the drilling tool 4 is at least four times that of the electromechanical transducer 1 for typical lengths of the drilling tool 4. The resonant vibration of the drilling tool 4 probably lasts little longer than the brief interval of 10-kc. impacts between the drilling tool 4 and the tip of the electromechanical transducer 1 (in the case of l=O-kc. electromechanical transducer).

FIG. 7 illustrates data from measurements of a typical drilling cycle indicating that, in the case of a 10- kc. electromechanical transducer 1, the drilling tool 5 is 1mpacted at a rate varying from 3.5ltc. to 10-kc. duringapproximately /3 of a cycle of oscillation 9 of the spr ngmass system, or second in a 50 c.p.s. oscillation. During the other /z of the cycle, the drilling tool 4 is not impacted by the tip of the electromechanical transducer 1.

Referring again to FIG. 7, it can be seen that there 1s illustrated the frequencies of the various elements of the present invention. FIG. 7, section A, illustrates the gross motion of the electromechanical transducer 1 and supporting structure as measured at the node 16 or the supporting structure 15 of the electromechanical transducer 1. This gross motion is related to the motion associated with the application of the intermittent static force to the electromechanical transducer 1 during the operation of the transducer during the drilling process. FIG. 7, section B, illustrates the axial motion of the tip of the electromechanical transducer 1 as superimposed on the gross motion of the electromechanical transducer 1 and its supporting structure 2 (see FIG. 7, section A). FIG. 7, section C, illustrates the period during which the drilling tool 4 is impacted. The drilling tool 4 is impacted during approximately /3 of the gross motion oscillatory cycle of said electromechanical transducer 1 as illustrated by the distance 9 in the figure. This impacting occurs at a rate of approximately 10-kc. when the drilling tool 4 is forced against the ti of the electromechanical transducer 1 and the refractory material 5. As illustrated, contact occurs approximately /3 of the time and no contact occurs /3 of the time, the period during which the drilling tool 4 is in free flight.

It has been found that the drilling rate using the system and method of the present invention varies with the dimensions of the drilling tool 4. It has been found that variation in the dimensions of the drilling tool 4 can have a substantial effect on the gross motion of the drilling tool 4. Alteration of the gross motion of the drilling tool 4 in turn affects the number of times the drilling tool 4 strikes the refractory material 5 per second. In the drilling process of the present invention, the length of the drilling tool 4 affects the resonant frequency of the drilling tool 4. This affects the drilling rates by as much as 3:1. This is attributable to the vibration of the drilling tool which effects removal of dust from the hole as it is being drilled in the refractory material 5. Reference is made to FIG. 6 which illustrates the manner with which the drilling rate varies with tool lenth.

Dilferences between conventional drilling tools and processes and the system and process of the present invention involve the nature of the respective tool geometries and the nature or form of the material removed during the drilling operation. The following table illustrates the difference between the conventional drilling operations and the system and process of the present invention.

1 1 Conventional drilling: Electromechanical drilling (1) Sharp ended tools Flat or planar tools. (2) Chips and dust formed Powder formed. (3) Chips and dust tend Powder usually ejected to remain in hole from hole. (4) Tool length of little Tool length affects significance drilling rate.

Although certain and specific embodiments of the present invention have been illustrated, modifications may be made to said invention to perform related functions without departing from the true spirit and scope thereof.

What we claimed is:

1. A method for anchoring a drilling tool in a refractory material utilizing a metal alloy comprising the steps of applying intermittent static force to an electromechanical transducer, applying vibratory-mechanical energy from said electromechanical transducer to said drilling tool to drill a hole wherein said drilling tool has a planar surface which contacts and drills said refractory material, removing said drilling tool after the drilling operation is completed, placing said metal alloy in said hole, placing said planar surface of said drilling tool in contact with said metal alloy, applying constant static force to said electromechanical transducer thereby generating heat in said drilling tool by high velocity friction and mechanical hysteresis thereby melting said metal alloy in said hole, and removing said electromechanical transducer from contact with said drilling tool thereby anchoring said drilling tool in said hole.

2. A method as set forth in claim 1 wherein the step of applying said intermittent static force to said electromechanical transducer further comprises transmitting said intermittent static force through said electromechanical transducer to said drilling tool and combining said intermittent static force with said vibratory-mechanical energy thereby fracturing said refractory material under said planar surface of said drilling tool thereby drilling said hole.

3. A method as described in claim 1 wherein said step of applying said constant static force to said electromechanical transducer when said drilling tool is in contact with said metal alloy which has been placed in said hole further comprises transmitting said constant static force through said electromechanical transducer to said drilling tool, whereafter said drilling tool ceases to penetrate said refractory material.

4. A method as described in claim 1 wherein said step of generating heat in said drilling tool further comprises exciting said drilling tool with vibratory-mechanical energy and combining the stresses created in said drilling tool resulting from applying said vibratory-mechanical energy with the stress resulting from applying said constant static force for a predetermined time thereby causing mechanical hysteresis, high-velocity friction, and the liberation of heat in said drilling tool.

5. A method as described in claim 1 wherein the step of melting said metal alloy further comprises the step of forcing the heated drilling tool to the bottom of said hole as heat from said heated tool and high-velocity friction melts said metal alloy and squeezes said drilling tool past the melted metal alloy thereby surrounding said drilling tool with said melted metal alloy.

6. A method as described in claim 5 wherein said step further comprises exciting said melted metal alloy with said vibratory-mechanical energy thereby penetrating said melted metal alloy into the interstices of said refractory material.

7. A method as described in claim 1 wherein said step of removing said electromechanical transducer from contact with said drilling tool further comprises allowing the melted metal alloy to cool and solidify thereby anchoring said drilling tool securely in said hole in said refractory material.

8. A method as described in claim 1 wherein said step of placing a mehtal alloy in said hole further comprises using a low-melting bismuth alloy whereby said bismuth alloy expands on solidifying.

9. A method for anchoring an inverted T shaped drilling tool, said tool having a hollow cylinder of a metal alloy positioned around the shank of said inverted T shaped drilling tool, in refractory material comprising the steps of applying intermittent static force to an electromechanical transducer, applying vibratory-mechanical energy from said electromechanical transducer to said inverted T shaped drilling tool, said lower portion of said inverted T shaped drilling tool having a planar surface which contacts and drills said refractory material, applying constant static force to said electromechanical transducer when said hole has been drilled to the desired depth, generating heat in said drilling tool, melting said metal alloy around said drilling tool in said hole, and removing said electromechanical transducer from contact with said drilling tool thereby anchoring said tool in said hole.

10. A method as described in claim 9 wherein said step of applying said intermittent static force to said electromechanical transducer further comprises transmitting said intermittent static force through said electromechanical transducer to said drilling tool and combining said intermittent static force with said vibratory-mechanical energy thereby fracturing said refractory material under said planar surface of said drilling tool thereby drilling said hole.

11. A method as described in claim 9 wherein said step of applying said constant static force to said electromechanical transducer when said drilling tool reaches the desired depth further comprises transmitting said constant static force through said electromechanical transducer to said drilling tool whereafter high-velocity friction occurs at the tool-refractory material interface and said drilling tool ceases to penetrate said refractory material.

12. A method as described in claim 9 wherein said step of generating heat in said drilling tool further comprises exciting said drilling tool with vibratory-mechanical energy thereby combining the stresses created in said drilling tool resulting from the applied vibratory-mechanical energy with the stress resulting from said applied constant static force, said combined stresses causing mechanical hysteresis and the liberation of heat in said drilling tool.

13. A method as described in claim 12 wherein said step of melting said metal alloy further comprises maintaining said constant static force and said vibratory-mechanical energy excitation until said metal alloy melted sufiiciently for said metal alloy to flow.

14-. A method as described in claim 13 wherein said step further comprises exciting said metal alloy with said vibratory-mechanical energy thereby penetrating said melted metal alloy into the interstices of said refractory material.

15. A method as described in claim 9 wherein the step of removing said electromechanical transducer from contact with said drilling tool further comprises allowing the melted metal alloy to cool and solidify thereby anchoring said drilling tool securely in said hole in said refractory material.

References Cited UNITED STATES PATENTS 3,184,353 5/1965 Balamuth 29432 3,282,315 11/1966 Zahodiakin 29432 3,431,593 3/1969 Miller 29525 3,477,115 11/1969 Martin 29432 JOHN F. CAMPBELL, Primary Examiner D. P. RODNEY, Assistant Examiner US. Cl. X.R. 77-65; 76107 

